红树林重金属污染生态学研究进展

红树林湿地,由于其固有的一些特性,能够大量接受来自潮汐、河水、地表径流所携带的重金属污染物.近30a来,红树林湿地重金属污染问题已引起了国内外学者们的极大关注,并对此进行了大量的研究.分别对重金属在红树林湿地中的分布与迁移、红树植物对重金属的生长响应及耐性机理等方面的研究进展和存在的问题进行了综述;此外,还对红树林湿地重金属净化效应的相关研究进行简要的概述.最后,对今后的研究趋势提出了一些看法.     

植物对重金属耐性的分子生态机理

植物适应重金属元素胁迫的机制包括阻止和控制重金属的吸收、体内螯合解毒、体内区室化分隔以及代谢平衡等。近年来,随着分子生物学技术在生态学研究中的深入应用,控制这些过程的分子生态机理逐渐被揭示出来。菌根、根系分泌物以及细胞膜是控制重金属进入植物根系细胞的主要生理单元。外生菌根能显著提高寄主植物的重金属耐性,根系分泌物通过改变根际pH、改变金属物质的氧化还原状态和形成络合物等机理减少植物对重金属的吸收。目前,控制菌根和根系分泌物重金属抗性的分子生态机理还不清楚。但细胞膜跨膜转运器已得到深入研究,相关金属离子转运器被鉴定和分离,一些控制基因如铁锌控制运转相关蛋白(ZIP)类、自然抵抗相关巨噬细胞蛋白(Nramp)类、P_1B-type ATPase类基因已被发现和克隆。金属硫蛋白(MTs)、植物螯合素(PCs)、有机酸及氨基酸等是植物体内主要的螯合物质,它们通过螯合作用固定金属离子,降低其生物毒性或改变其移动性。与MTs合成相关的MT-like基因已经被克隆,PCs合成必需的植物螯合素合酶(PCS), 即γ-Glu-Cys二肽转肽酶(γ-ECS) 的编码基因已经被克隆,控制麦根酸合成的氨基酸尼克烟酰胺(NA)在重金属耐性中的作用和分子机理也被揭示出来。ATP 结合转运器(ABC)和阳离子扩散促进器(CDF) 是植物体内两种主要膜转运器,通过它们和其它跨膜方式,重金属被分隔贮藏于液泡内。控制这些蛋白转运器合成的基因也已经被克隆,在植物中的表达证实其与重金属的体内运输和平衡有关。热休克蛋白(HSP)等蛋白类物质的产生是一种重要的体内平衡机制,其分子机理有待进一步研究。重金属耐性植物在这些环节产生了相关响应基因或功能蛋白质,分子克隆和转基因技术又使它们在污染治理上得到了初步的应用。     

污染胁迫下的蚯蚓蛋白质组学研究进展

随着蛋白质组学的发展和每年有大量环境污染物进入土壤环境中,污染胁迫模式动物的相关生物标志物受到日益关注。蚯蚓,作为土壤中最大的无脊椎动物,是研究和评价土壤生态污染良好的模式动物。研究蚯蚓的蛋白质组学,对于寻找环境生态污染相关生物标志物和阐明生态毒理学机制有着十分重要的现实意义。目前已知的污染胁迫下蚯蚓蛋白质组学研究,提供了几个特定污染物胁迫蚯蚓的蛋白表达谱。这些蛋白涉及许多生物学过程,例如信号传导、糖酵解、能量代谢、分子伴侣和转录调节,提示了相关污染物可能的生态毒理学机制,有望成为潜在的生物标志物,用于有毒污染物的监测,但其特异性需要进一步试验的验证。对蚯蚓受污染胁迫的蛋白质组表达谱及潜在生物标志物进行简要综述。     

沉水植物对重金属的吸收净化和受害机理研究进展

沉水植物对重金属的积累净化和受害机理研究主要集中在4个方面：（1）沉水植物对重金属（包括放射性物质）的吸收、积累和净化作用;（2）沉水植物对重金属的抗性强弱和机制;（3）沉水植物用于监测水体的重金属污染;（4）沉水植物的重金属胁迫机制,包括重金属对植物形态和显微结构的损伤,对植物抗氧化酶系统的影响,对植物的叶绿素、蛋白质以及光合与呼吸作用等生理生化指标的影响,植物对重金属的吸附和转运动力学,以及Zn对Cd毒害的拮抗等。     

高等植物重金属耐性与超积累特性及其分子机理研究

由于重金属污染日益严重, 重金属在土壤_植物系统中的行为引起了人们的高度重视。高等植物对重金 属的耐性与积累性, 已经成为污染生态学研究的热点。近年来, 由于分子生态学等学科的发展, 有关植物对重金属的解毒和耐性机理、重金属离子富集机制的研究取得了较大进展。高等植物对重金属的耐性和积累在种间和基因型之间存在很大差异。根系是重金 属等土壤污染物进入植物的门户。根系分泌物改变重金属的生物有效性和毒性, 并在植物吸收重金属的过程中发挥重要作用。土壤中的大部分重金属离子都是通过金属转运蛋白进入根细胞, 并在植物体内进一步转运至液泡贮存。在重金属胁迫条件下植物螯合肽 (PC) 的合成是植物对胁迫的一种适应性反应。耐性基因型合成较多的PC, 谷胱甘肽 (GSH) 是合成PC的前体, 重金属与PC螯合并转移至液泡中贮存, 从而达到解毒效果。金属硫蛋白 (MTs) 与PC一样, 可以与重金属离子螯合, 从而降低重金属离子的毒性。该文从分子水平上论述了根系分泌物、金属转运蛋白、MTs、PC、GSH在重金属耐性及超积累性中的作用, 评述了近 10年来这方面的研究进展, 并在此基础上提出存在的问题和今后研究的重点。     

植物修复的生物学机制

随着现代化工业的发展,全球向土壤和环境中排放的重金属逐年增加。重金属污染已日益成为威胁人类健康和影响人类生活质量的严重环境问题和社会问题。这一问题可部分通过植物修复技术得以解决。植物修复技术是依据植物从环境中积累重金属元素和化合物的能力及其将这些有毒物质在植物体内代谢成无毒生物小分子的能力而建立的新的生物技术。本篇综述主要论及利用植物修复技术解决重金属污染的生物学机制。     

中国近海持久性毒害污染物研究进展

持久性毒害污染物具有三致效应和遗传毒性,对近海生态环境危害极大。持久性毒害污染物主要通过人海河流和沿岸直排输送人海,主要赋存于近海沉积体系。持久性毒害污染物在沉积物分布累积主要受到沉积环境的影响,包括人海河流径流量、输沙量、水动力、河口海湾冲淤演变等,以及其自身物理化学性质和沉积物性质如颗粒物大小和有机质含量等。不同海区的研究表明,重金属污染整体上较轻微,胶州湾沉积物Cu、As污染较其它地区严重,珠江口盐沼Cd、Zn污染最为严重;近海沉积物有机污染主要集中在工业活动密集的珠江三角洲及邻近海域、长江口及闽江口海区,多氯联苯（PCBs）污染以珠江三角洲最为严重,有机氯农药（OCPs）污染在东南部河口及邻近海区较为严重。在明确持久性毒害污染物在不同沉积环境下差异和共性的基础上,提出若干今后需加强的研究,包括污染物迁移转化规律、重金属化学形态分析、微生物降解机制和污染物相互作用,等。     

道路交通污染对昆虫的影响

综述了国内外近年来道路交通污染及其空气污染物对昆虫影响的研究状况。介绍了交通污染的现状,阐述了汽车尾气中不同污染物,包括二氧化硫（SO₂）、氮氧化物（NO_x,包括NO和NO₂）、碳氧化物（CO_x,包括CO和CO₂）、挥发性有机物（VOCs）、酸雨和臭氧（O₃）,以及细颗粒扬尘等污染物对昆虫发生和种群适合度等的影响,并分析了交通污染影响昆虫的作用机理,指出了国内今后该领域的研究方向。此外,道路交通污染对周边生物环境也会造成相关的生态影响。今后应加强生态道路建设,减轻交通污染对路域生态系统的影响。     

木本植物对大气重金属污染物耐性的研究

本文在污染现场调查研究、试验研究和单一毒物接触试验的大量数据基础上,论述了木本植物对大气重金属污染物一一铅、镉、铜、锌的耐性。查明了大气重金属污染物引起叶片可见伤害症状需要很高的剂量。糖槭以2000ppm硝酸铅溶液浸泡涂抹枝叶,三天后出现轻度可见伤害症状,叶中铅积累量高达802ppm。旱柳以500ppm氯化镉溶液浸泡涂抹枝叶,叶中积累量达66ppm,十天内未出现可见症状。大气重金属污染物——铅、镉、铜、锌对叶片造成的急性伤害症状是相似的,而与土壤中相同污染物引起的急性伤害具有差别。木本植物对大气重金属污染物的耐性很强,在以大气重金属污染为主的复合污染现场,一些幼龄树木的叶片吸铅量达500—800ppm,超过背景浓度的120倍;吸镉量10—18ppm,超过背景浓度的139倍,吸铜量100—239ppm,超过背景浓度的5—12倍,吸锌量500—700ppm,超过背景浓度的9—20倍只出现较轻的受害症状。在相对清洁区,对幼树叶片进行单一毒物接触试验,一些主要绿化树木的叶片吸铅量达200—600ppm,吸镉量20—60ppm并不出现可见症状。木本植物对大气重金属污染物具有较强的耐性,因而为生物防治大气重金属污染开辟了广阔的前景。     

碳纳米材料的环境行为及其对环境中污染物迁移归趋的影响

碳纳米材料具有广阔的应用前景,近年来已成为一大研究热点.工程碳纳米材料的大量生产和使用将不可避免地造成这些材料向环境中的释放,可能带来环境和生态风险.一方面,碳纳米材料本身具有环境毒性,另一方面碳纳米材料对环境中有毒有害污染物有较强的吸附性能,因此会影响污染物迁移转化等环境行为.目前,对碳纳米材料生态风险的研究主要集中于碳纳米材料对生物体可能的毒性,而对其自身环境行为以及影响污染物迁移归趋等方面的研究较少.本文简要概述了碳纳米材料的来源、暴露途径、环境行为以及对污染物迁移归趋的影响,阐述了这些研究对于评估碳纳米材料的环境和生态风险所具有的重要意义.     

Dualities in plant tolerance to pollutants and their uptake and translocation to the upper plant parts

There is a duality in plant tolerance to pollutants and its response to the pollutants’ stress.On the one hand some plants, (hyper)tolerant to heavy metals, are able to hyperaccumulate these metals in shoots, which could be beneficial for phytoremediation purposes to clean-up soil and water. On the other hand tolerant food crops, exposed to heavy metals in their growth medium, may be dangerous as carriers of toxic metals in the food chain leading to food toxicity. There is an additional duality in plant tolerance to heavy metals and that is in food crops that are tolerant and/or hyperaccumulators, which could be used on one hand for phytoremediation, under controlled conditions and on the other hand for food fortification with essential metals.Similarly, plants are also exposed to a large number of xenobiotic organic pollutants. Because they generally cannot avoid these compounds, plants take up, translocate, metabolize and detoxify many of them. There is a large variability in tolerance (defence) mechanisms against organic pollutants among plant species. This includes production of reductants but also scavenger molecules like ascorbate and glutathione and expression of the P-450 defence system, and superfamilies of the enzymes glutathione- and glucosyl-transferases. Again, with view to organic pollutants, plant detoxification mechanisms might well protect the plant itself, but produce compounds with some deleterious potential for other organisms.In this review we discuss these dualities on the basis of examples of agricultural and ‘wild’ species exposed to metal contaminants (mainly Cd) and organic pollutants. Differences in uptake and translocation of various pollutants and their consequences will be considered. We will separately outline the effects of the organic and non-organic pollutants on the internal metabolism and the detoxification mechanisms and try to indicate the differences between both types of pollutants. Finally the consequences and solutions of these dualities in plant tolerance to pollutants will be discussed.     

鱼类对重金属胁迫的分子反应机理

水体中浓度超标的重金属对鱼类的正常生命活动产生了严重影响,甚至导致鱼类的死亡.鱼体受重金属离子胁迫时体内会产生一系列相关基因的表达变化,并合成相关的蛋白和酶,如热激蛋白、金属硫蛋白、转运铁蛋白、谷胱甘肽转移酶、过氧化氢酶、超氧化物歧化酶等以应对重金属对机体产生的危害.这是生物体对环境的一种应激保护性反应,是生物体对周围环境中过量重金属的一种防御性机制.通过鱼类在重金属胁迫下组织中相关基因的表达可以从分子水平上来阐述有毒物质对鱼体产生的影响.综述了重金属离子胁迫下鱼类机体的分子反应机理.     

The role of aryl hydrocarbon receptor and the reactive oxygen species in the modulation of glutathione transferase by heavy metals in murine hepatoma cell lines

Glutathione transferase (GST) is a phase II detoxifying enzyme that plays a protective mechanism against oxidizing substances and toxic contaminants. Among these contaminants, heavy metals and polycyclic and halogenated aromatic hydrocarbons (PHAHs) have been shown to exert their toxic effects through the modulation of detoxifying enzymes, including the GSTs. Recently, we showed that heavy metals particularly Hg2+, Pb2+, and Cu2+ modulate the expression of phase II detoxifying enzymes such as NAD(P)H:quinone oxidoreductase 1 and Gsta1 in a concentration- and time-dependent manner. However, the effect of heavy metals and their potential interactions with aryl hydrocarbon receptor (AhR) ligands, PHAHs, on total Gst activity is still unknown. In the current study, we have investigated the effects of Hg2+, Pb2+, and Cu2+ in the absence and presence of four AhR ligands on the total Gst activity and reactive oxygen species (ROS) production in wild-type and AhR-deficient Hepa 1c1c7 cells. Our results showed that Hg2+ and Cu2+, but not Pb2+, significantly induced Gst activity in wild-type cells, whereas all metals induced the Gst activity in AhR-deficient cells. The induction of Gst activity by heavy metals was strongly correlated with an increase in the ROS production in wild-type, but not in AhR-deficient cells. Co-administration of heavy metals with AhR ligands differentially modulated Gst activity, in that co-exposure to Hg2+ plus AhR ligands could be beneficial in protecting against cytotoxicity as demonstrated by the increase in Gst activity with a proportional decrease in ROS production. Whereas co-exposure to Cu2+ plus AhR ligands was more toxic in that a decrease in Gst activity and an increase in oxidative stress of the cell were observed. We concluded that heavy metals differentially modulate the Gst activity through oxidative stress- and AhR-mediated mechanisms.     

硅藻重金属污染生态学研究进展

硅藻是水生生态系统健康的指示生物之一,对环境变化极为敏感,某些典型硅藻已应用于指示水体重金属污染.本文围绕地表水重金属污染,从毒性效应、生物吸附和累积、生态适应机制及生物指示与生态修复作用等方面,综述了硅藻重金属污染生态学研究进展,阐述重金属污染下硅藻的生长趋势和硅壳形态的变化,硅藻对重金属生物吸附和生物累积的差别,硅藻对重金属的表面络合和离子交换等生态适应机制,以及硅藻对水体重金属污染的指示作用和生态修复作用,为水生生态系统的重金属污染防治与预警技术提供科学依据.     

Biochemical changes and adaptive strategies of plants under heavy metal stress

Heavy metal contamination of soil, aqueous waste stream and ground water causes major environmental and human health problems. Heavy metals are major environmental pollutants when they are present in high concentration in soil and show potential toxic effects on growth and development in plants. Due to unabated, indiscriminate and uncontrolled discharge of hazardous chemicals including heavy metals into the environment, plant continuously have to face various environmental constraints. In plants, seed germination is the first exchange interface with the surrounding medium and has been considered as highly sensitive to environmental changes. One of the crucial events during seed germination entails mobilization of seed reserves which is indispensable for the growth of embryonic axis. But, metabolic alterations by heavy metal exposure are known to depress the mobilization and utilization of reserve food by affecting the activity of hydrolytic enzymes. Some plants possess a range of potential mechanisms that may be involved in the detoxification of heavy metals by which they manage to survive under metal stress. High tolerance to heavy metal toxicity could rely either on reduced uptake or increase planned internal sequestration which is manifested by an interaction between a genotype and its environment. Such mechanism involves the binding of heavy metals to cell wall, immobilization, exclusion of the plasma membrane, efflux of these toxic metal ions, reduction of heavy metal transport, compartmentalization and metal chelation by tonoplast located transporters and expression of more general stress response mechanisms such as stress proteins. It is important to understand the toxicity response of plant to heavy metals so that we can utilize appropriate plant species in the rehabilitation of contaminated areas. Therefore, in the present review attempts have been made to evaluate the effects of increasing level of heavy metal in soils on the key behavior of hydrolytic and nitrogen assimilation enzymes. Additionally, it also provides a broad overview of the strategies adopted by plants against heavy metal stress.     

PHYCOLOGY AND HEAVY-METAL POLLUTION

1. All heavy metals, including those that are essential micronutrients (e.g. copper, zinc, etc.), are toxic to algae at high concentrations. 2. One characteristic feature of heavy-metal toxicity is the poisoning and inactivation of enzyme systems. Many of the physiological and biochemical processes, viz., photosynthesis, respiration, protein synthesis and chlorophyll synthesis, etc., are severely affected at high metal concentrations. 3. Some algae inhabit waters chronically polluted with heavy-metal-laden wastes from mining and smelting operations; Nodularia sp., Oscillatoria sp., Cladophora sp., Hormidium sp., Fucus sp. and Laminaria sp., etc., occur in metal-rich waters. These algal forms are probably more capable of combating the toxic levels of heavy metals and this attribute is a result of physiological and/or genetic adaptations. The sensitivity or tolerance to heavy metals varies amongst different algae. The phenomena of multiple tolerance and co-tolerance may be exhibited by some algae. 4. Heavy-metal pollution causes reduction in species diversity leading to the dominance of a few tolerant algal forms. The primary productivity also decreases after metal supplementation. 5. The uptake and accumulation of heavy metals can be active (energy-dependent), passive (energy-independent), or both. 6. Heavy metals can be safely stored as intranuclear complexes by some algae. Notwithstanding this, some changes in the cell wall can enable the algae to tolerate heavy metals by checking the entry of the metals (exclusion mechanism). 7. The metal content of algae growing in a waterbody may yield valuable information for simulating heavy metal pollution: several species of Cladophora and Fucus have been extensively used for this purpose. 8. Several factors affect and determine toxicity of heavy metals to algae. At low pH, the availability of heavy metals to algae is greatly increased, as a consequence of which pronounced toxicity is evident. Hard waters decrease metal toxicity. Some ions, e.g., calcium, magnesium and phosphorus, can alleviate toxicity of metals. 9. The presence of other metals can influence toxicity of a heavy metal through simple additive effect or by synergistic and antagonistic interactions. Similarly, other pollutants can influence heavy-metal toxicity. 10. The toxicity of heavy metals depends upon their chemical speciation. Various ionic forms of a metal characterized by different valency states, may be differentially toxic to a test alga. 11. Amino acids, organic matter, humic acids, fulvic acid, EDTA, NTA, etc. can complex with heavy metals and render them unavailable. This may eventually lead to less toxicity. 12. Heavy-metal toxicity largely depends upon algal population density: the denser the population the more numerous the cellular sites available, leading to decreased toxicity.     

Effects of Bioavailable Heavy Metal Species,Arsenic, and Acid Drainage from Mine Tailings on a Microbial Community Sampled Along a Pollution Gradient in a Freshwater Ecosystem

Sediment and water samples representing a pollution gradient in a long, narrow lake polluted at one end by heavy metals, arsenic, and acid drainage from mine tailings, together with samples from an unpolluted reference lake, were analyzed to determine effects of pollutants on the microbial community of the polluted lake. Ribosomal ribonucleic acid, fatty acid, and phospholipid analyses, along with assays of CO₂ production, denitrification, and enzyme activities, were performed to characterize the microflora; and environmental conditions were defined by various physicochemical analyses, including determination of bioavailable metal species. Mine waste pollution fostered the growth of Holophagal Acidobacteria, green sulphur bacteria, and α-Proteobacteria but inhibited numerous other types of microorganisms, reducing the overall productivity, biomass, and biodiversity of the microflora. The beneficial effects imply toleration of pollutants, suppression of competing or antagonistic species, and utilization of biogenic sulphide; and the toxic effects are attributable to bioavailable metals, arsenic, and sulphuric acid produced by oxidation of sulphides. The bioavailability and toxicity of sediment-bound metals were evidently increased by acidification, elevation of sediment Eh, and inhibition of metal-immobilizing bacteria by pollutants but were decreased by metal-scavenging oxyhydroxides, sulphide, and organic matter. Metal toxicity also depended on specific metal properties (e.g., electronegativity), providing a basis for inferring mechanisms of toxicity and oxidation states of metals and explaining differences in relative toxicity. The pollutants harmed the ecosystem as a whole by inhibiting microorganisms that performed crucial ecological functions, notably oxygen-releasing photosynthesis, decomposition and humification of organic matter, nutrient recycling, and control of metal availability.     

Pollution biomarkers in estuarine animals: critical review and new perspectives

In this review, recent developments in monitoring toxicological responses in estuarine animals are analyzed, considering the biomarker responses to different classes of pollutants. The estuarine environment imposes stressful conditions to the organisms that inhabit it, and this situation can alter their sensitivity to many pollutants. The specificity of some biomarkers like metallothionein tissue concentration is discussed in virtue of its dependence on salinity, which is highly variable in estuaries. Examples of cholinesterase activity measurements are also provided and criteria to select sensitive enzymes to detect pesticides and toxins are discussed. Regarding non-specific biomarkers, toxic responses in terms of antioxidant defenses and/or oxidative damage are also considered in this review, focusing on invertebrate species. In addition, the presence of an antioxidant gradient along the body of the estuarine polychaete Laeonereis acuta (Nereididae) and its relationship to different strategies, which deal with the generation of oxidative stress, is reviewed. Also, unusual antioxidant defenses against environmental pro-oxidants are discussed, including the mucus secreted by L. acuta. Disruption of osmoregulation by pollutants is of paramount importance in several estuarine species. In some cases such as in the estuarine crab Chasmagnathus granulatus, there is a trade off between bioavailability of toxicants (e.g. metals) and their interaction with key enzymes such as Na(+)-K(+)-ATPase and carbonic anhydrase. Thus, the metal effect on osmoregulation is also discussed in the present review. Finally, field case studies with fish species like the croaker Micropogonias furnieri (Scianidae) are used to illustrate the application of DNA damage and immunosuppressive responses as potential biomarkers of complex mixture of pollutants.